1. Field of the Invention
This invention relates to a work fixture having a workpiece clamp, and more particularly to a fixture such as a welding fixture wherein one or more workpiece clamps automatically release and move clear of a tool, such as a welding head, when the clamp is triggered by approach of the tool or welding head.
2. Description of the Prior Art
Brantingham U.S. Pat. No. 1,795,036, May 20, 1930 discloses a welding fixture wherein the top wall of a sheet metal refrigerator liner is clamped against a horizontal support base template by a pivoted outside clamping template plate. The outside template plate pivots about a horizontal axis and the template is operated by a manual handle that is raised or lowered to actuate a toggle linkage assembly for the clamping template plate.
Archea U.S. Pat. No. 1,938,771, Dec. 12, 1933 discloses a milling machine formed with fluid pressure operated sliding clamps projecting up through a fixture plate that supports the workpiece. Clamp release valve levers are operated by dogs mounted on the reciprocating milling machine table.
Lampe U.S. Pat. No. 2,567,436, Sept. 11, 1961 discloses a toggle clamp wherein clamping is effected by reciprocating a rod through an over-center linkage operated by a manual handle.
Reason U.S. Pat. No. 2,888,052, May 26, 1959 discloses a bench mounted manual clamp screw supported on a manually swingable clamping arm that overhangs the workpiece.
Bachtel, Jr. U.S. Pat. No. 3,924,844, Dec. 9, 1975 discloses a toggle clamp lock wherein a pivoted swinging clamp arm is retracted by a manually operated pivoted handle with the handle and clamp arms swinging in the same plane.
McPherson U.S. Pat. No. 3,237,463, Mar. 1, 1966 discloses a double acting plunger clamp wherein a sliding clamping plunger is reciprocated by a bell crank manual handle and a bridge link.
Blatt U.S. Pat. No. 3,782,712, Jan. 1, 1974 discloses a toggle clamp resembling that of Brantingham except that the handle can be manually operated to pivot the clamp arm extirely clear of the fixture. The handle and clamp arm pivot axes are parallel.
Fraser et al. U.S. Pat. No. 3,912,251, Oct. 14, 1975 discloses a toggle clamp that is basically the same as that of McPherson U.S. Pat. No. 3,237,463.
Kato U.S. Pat. No. 4,141,543 discloses (FIG. 7) a pivoted clamp arm and a pivoted manual actuated handle where the pivot axes are parallel. The device is basically like that of Blatt U.S. Pat. No. 3,782,712.